We propose a model Hamiltonian for van der Waals tunnel transistors (vdW-TFETs) relying on few physical parameters calibrated against density functional theory (DFT) band structure calculations. Based on this model, we develop a fully 3-D nonequilibrium Green’s function simulator including electron-phonon scattering, and we investigate some fundamental aspects and design challenges related to vdW-TFETs based on single-layer MoS2 and WTe2. In particular, we devote a specific analysis to the impact of top gate alignment and back-oxide thickness on the device performance. Our results suggest that the vdW-TFETs can provide very small values of subthreshold swing (SS) and fairly good ON-state current. However, these devices also pose specific design challenges related to the geometrical features of gated regions, and their ultimate SS may be lower limited by inelastic phonon scattering.
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